Particle size, pollutant

Rulkens WH and Bruning H (1995) Clean-up possibilities of contaminated soil by extraction and wet classification effect of particle size, pollutant properties and physical state of pollutants. In Van den Brink WJ, Bosman R, Arendt E, eds. Contaminated Soil 95, pp. 761-773. Kluwer Academic Publ, Dordrecht. 

Aerosol Dynamics. Inclusion of a description of aerosol dynamics within air quaUty models is of primary importance because of the health effects associated with fine particles in the atmosphere, visibiUty deterioration, and the acid deposition problem. Aerosol dynamics differ markedly from gaseous pollutant dynamics in that particles come in a continuous distribution of sizes and can coagulate, evaporate, grow in size by condensation, be formed by nucleation, or be deposited by sedimentation. Furthermore, the species mass concentration alone does not fliUy characterize the aerosol. The particle size distribution, which changes as a function of time, and size-dependent composition determine the fate of particulate air pollutants and their... 

FIG. 14-128 Superheated high-pressure hot-water requirements for 99 percent collection as a function of particle size in a two-phase eductor jet scnihher To convert gallons per 1000 cuhic feet to cuhic meters per 1000 cuhic meters, multiply hy 0.1.34. [Gardenier, J. Air Pollut. Control Assoc., 24, 954 (1974).]... 

Denison (12) gave a table of field observations of washout ratios. The values for various pollutants range from less than 100 to more than 4000. These values are a function of particle size and rainfall intensity, generally decreasing with the latter and increasing with the former. 

Aircraft can take vertical temperature soundings and can measure air pollutant and tracer concentrations and turbulence intensity. Airborne lidar can measure plume heights, and integrating nephelometers can determine particle size distributions. 

The concentration of indoor pollutants is a function of removal processes such as dilution, filtration, and destruction. Dilution is a function of the air exchange rate and the ambient air quality. Gases and particulate matter may also be removed from indoor air by deposition on surfaces. Filtration systems are part of many ventilahon systems. As air is circulated by the air-conditioning system it passes through a filter which can remove some of the particulate matter. The removal efficiency depends on particle size. In addition, some reactive gases like NOj and SOj are readily adsorbed on interior surfaces of a building or home. 

Small solid particles, present in dust and grit emissions, have very low settling velocities (Table 4.4) The collection efficiencies of simple cyclones are tlierefore, as shown in Figure 17.3, relatively low. Fabric filters, electrostatic precipitators or wet scrubbers may be required to remove particles <5 pm in size with an acceptable efficiency. Therefore the cost of pollution control inevitably increases when dealing with particle size distributions skewed towards the lower end. 

Ash particles produced in coal combustion are controlled by passing the flue gases through electrostatic precipitators. Since most of the mass of particulate matter is removed by these devices, ash received relatively little attention as an air pollutant until it was shown that the concentrations of many toxic species in the ash particles increase as particle size decreases. Particle removal techniques become less efiective as particle size decreases to the 0.1-0.5 pm range, so that particles in this size range that escape contain disproportionately high concentrations of toxic substances. 

Considerable work has been done on the behavior of pollutant species at air-water and air-soil interfaces. For example, wet and diy deposition measurements of various gaseous and particulate species have been made over a wide range of atmospheric and land-cover conditions. Still, the problem is of such complexity that species-dependent and particle-size-dependent rates of transfer from the atmosphere to water and soil surfaces are not completely understood. There is much to be learned about pollutant transfer at water-soil interfaces. Concern about groundwater contamination by mineral... 

Examples of industrial chemical waste are given in Table 13.1. Common industrial sources of pollution are given in Table 13.2. Since waste can result in pollution, the two terms are often used synonymously. Wastes can be in the form of solid, liquid or gas, or any combination, e.g. solid waste comprises liquid slurries, sludges, thixotropic solids and solids of varying particle sizes. Typical examples are given in Table 13.3. 

This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers. The removal of air pollutants is achieved by the use of condensation to increase pollutant particle size, followed by inertial interception. Condensation scrubbers are typically intended to control fine PM with an aerodynamic diameter of between approximately 0.25 and 1.0 pm. 

This 10-year longitudinal study is focused on the potential associations between ambient air pollution and respiratory health in children. The objectives are to document the respiratory growth of study participants, to assess whether ambient pollutants play a role in respiratory health, and to identify which pollutants are responsible for any observed effects. Ambient air quality is being monitored in each of twelve communities by centrally located regional stations, CA, which also collect standard meteorological data. Gaseous pollutants are monitored continuously, while ambient particle concentration and size are determined by a number of approaches. Additional exposure assessment occurs because of the establishment of the Particle Center, including more extensive particle size number, surface area, and volume distribution measurements. 

One of the newest particle sizing techniques is light scattering. This technique is used to measure particle size distribution, colloid behavior, particle size growth, aerosol research, clean room monitoring, and pollution monitoring. 

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